Signal detection for vaccine side effects that have not been specified in advance


  • Alexander M. Walker MD, DrPH

    Corresponding author
    1. World Health Information Science Consultants, LLC, Newton, MA, USA
    2. Department of Epidemiology, Harvard School of Public Health, Boston MA, USA
    • WHISCON, Riverside Center, Suite 2-400, 275 Grove Street, Newton, MA 02466, USA.
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  • There are no relevant financial considerations to disclose.


An information-theoretic definition of similarity proposed by Dekang Lin in 1998 appears to have attractive properties for identifying medically similar cases in a large database. Examination of similar cases that appear following vaccination may provide a way of detecting previously unexpected associations. A key element here is the inclusion of shared time-since-vaccination as a dimension of similarity while considering concordance on many other features. The system is potentially much more sensitive to patterns with multiple features than are very large, high-dimension contingency tables. Copyright © 2009 John Wiley & Sons, Ltd.